PROJECT REPORT

ON

MICRO CONTROLLER BASEDTRAFFIC LIGHT CONTROLLER

Department of Electronics & Communication EngineeringGURU NANAK INSTITUTE OF TECHNOLOGY

SUBMITTED BY- ANKITA MUKHERJEE, ARGHA MUKHERJEE, ARGHADEEP CHOUDHURY, MAINAK NANDI,NABANITA MANNA

Project Report on

Microcontroller Based

Traffic Light Controller

CONTENTS

1. ABSTRACT

2. INTRODUCTION

3. FLOW CHART

4. BLOCK DIAGRAM AND EXPLANATION

5. CIRCUIT DIAGRAM

6. HARDWARE DESCRIPTION

™ POWER SUPPLY

™ MICROCONTROLLER UNIT

™ LIGHT EMITTING DIODE (LED)

™ DISPLAY

7. COMMON CATHODE 7 SEGMENT

8. SOFTWARE

9. COMPONENTS REQUIRED

10. FUTURE SCOPE

11. BIBLIOGRAPHY

1. ABSTRACT

Vehicular traffic at intersecting streets is typically controlled by traffic control lights.

The function of traffic lights requires sophisticated control and coordination to ensure

that traffic moves as smoothly and safely as possible.

In recent days electro-mechanical controllers are replaced by electronic circuits. The

accuracy & fault tolerant drive towards electronic circuits.

This project is developed to meet the requirements of solid state traffic light controller

by adopting microcontroller as the main controlling element, and led’s as the indication

of light. A micro controller is interfaced to led’s provide for centralized control of the

traffic signals. Microcontroller is programmed in such a way to adjust their timing and

phasing to meet changing traffic conditions. The circuit besides being reliable and

compact is also cost effective.

2. INTRODUCTION

Traffic congestion is a severe problem in many modern cities around the world.

Traffic congestion has been causing many critical problems and challenges in the major

and most populated cities. To travel to different places within the city is becoming more

difficult for the travelers in traffic. Due to these congestion problems, people lose time,

miss opportunities, and get frustrated. Traffic congestion directly impacts the companies.

Due to traffic congestions there is a loss in productivity from workers, trade opportunities

are lost, delivery gets delayed, and thereby the costs goes on increasing.

To solve these congestion problems, we have to build new facilities &

infrastructure but at the same time make it smart. The only disadvantage of making new

roads on facilities is that it makes the surroundings more congested. So for that reason

we need to change the system rather than making new infrastructure twice. Therefore

many countries are working to manage their existing transportation systems to improve

mobility, safety and traffic flows in order to reduce the demand of vehicle use.

The project uses simple Electronic components such as LED as TRAFFIC LIGHT

indicator and a MICROCONTROLLER for auto change of signal after a pre-specified

time interval.

This system uses 8051 microcontroller , 7-segments and LED’s for indication. The

LED’s which was used as lights was connected to the Microcontroller by means of

common Anode configuration. In this configuration the Microcontroller was used to sink

the current from the LED to its ports. That means logic 0 signal in the Microcontroller

switches the LED ON and logic 1 signal switches the LED off. Here we are using 6

MHz crystal for the 8051 Microcontroller operation and you can use upto 12MHz

crystal with this controller.

3. FLOWCHART

Start

InitializeTime0 as Timer

Move next signalingdata onto the portpins & start the

timer

Load DelayValue inTimer

Update the 7-segmentdisplay for

everyminute

YesIs

Nothe delaycompleted?

4. BLOCK DIAGRAM

7 – SEGMENTDISPLAY

MICRO

CONTROLLER(AT89C51) TRAFFIC

LIGHTS

+5VUNIT

POWER SUPPLY

5. CIRCUIT DIAGRAM

6. HARDWARE DESCRIPTION

(a) POWER SUPPLY:

Transformer Rectifier Filter Regulator

Almost all electronic circuits required Dc power supply. Dc power supply is a

circuit which converts the Ac wave form of power lines to direct voltage of constant

amplitude. An ideal regulated power supply is designed to provide a pre- determined Dc

voltage which is independent of the current drawn from the source. These circuits are

special class of feedback amplifiers. All the benefits of 'ICs' are thus obtained: excellent

performance, small size, ease of use, low cost, high and reliability.

An unregulated power supply has many disadvantages due to which it is not sufficient for many applications

• Poor regulation

• Dc out put voltage varies with the ac in put

• Dc out put voltage variation varies with temperature because of semi conductors

used To over come the above disadvantages we depend up on regulated power

supply. Regulated power supplies have internal short circuit protection, thermal

shut down and safe operation of output transistor.

TRANSFORMER

A transformer is a device which step-up (or) step-down the electrical quantities

according to the need. It adjusts the Ac level so that the appropriate Dc amplitude is

achieved. Its load handling capacity must be sufficient to supply the load and account for

the losses in the rectifier, filter and regulator. The turn’s ratio is determined by the output

level required relative to the ac input amplitude.

BRIDGE RECTIFIER

The circuit consists of four diodes (1N4007) in which at a time only two diodes

conduct. Each diode has only transformer secondary voltage across it on the inverse

cycle. This circuit model allows us to have the dc current to flow for the both cycles of Ac

input. The bridge circuit is thus suitable for high voltage application.

FILTERS

The use of Filters is to smoothen the waveform by eliminating the ac components

from the rectifier circuits basically capacitors are being connected in shunt. The action of

the system occurs as the capacitor stores energy during the conduction period and

delivers this energy to the load during non conducting period .In this way, the time

during which the current passes through the load is prolonged and the ripple is

considerably decreased .

The ripple voltage is defined as the deviation of the load voltage from its average

Dc value. Input capacitor is required to cancel inductive effects associated with long

power distribution leads out put capacitors improve the transient response.

REGULATOR

They maintain a constant voltage level independent of load condition or

variation in the amplitude of the Ac supply .An example of regulator is LM78xx series It

is the three terminal device with input (1) , ground(2), output(3) as its terminals. The

voltage required for micro controller is 5V. Hence LM7805 voltage regulator is used.

These devices require no adjustments and have an output preset by manufactures to

industry standard voltages of 5, 6, 8, 12, 15, 18, 24V.

Zener regulator is incorporated for maintaining 12v regulated output used for sensing probes and Electromagnetic relay.

(b) MICRO-CONTROLLER UNIT:

Micro-controller unit is constructed with AT89C51 Micro-controller chip. The

AT89C51 is a low power, higher performance CMOS 8-bit microcomputer with 4K bytes

of flash programmable and erasable read only memory (PEROM). Its high-density non-

volatile memory compatible with standard MCS-51 instruction set makes it a powerful

controller that provides highly flexible and cost effective solution to control applications.

Micro-controller works according to the program written in it. The program is

written in such a way, so that this controller energizes or de-energizes the relays

according to the information received by the pushbuttons and the sensing probe.

The 8051 series of microcontrollers are highly integrated single Chip

microcomputers with an 8-bit CPU, memory, interrupt controller, timers, Serial I/O and

digital I/O on a single piece of silicon. The 8051 is an 8-bit Machine. Its memory is

organized in bytes and practically all its instruction deal with byte quantities. It uses an

Accumulator as the primary register for instruction Results. Other operands can be

accessed using one of the four different addressing modes available: register implicit,

direct, indirect or immediate. Operands reside in one of the five memory spaces of the

8051.

The five memory spaces of the 8051 are: Program Memory, External Data Memory, Internal Data Memory, Special Function Registers and Bit Memory.

The Program Memory space contains all the instructions, immediate data and

constant tables and strings. It is principally addressed by the 16-bit Program Counter

(PC), but it can also be accessed by a few instructions using the 16-bit Data Pointer

(DPTR). The maximum size of the Program Memory space is 64K bytes. Several 8051

family members integrate on-chip some amount of either masked programmed ROM or

EPROM as part of this memory.

The External Data Memory space contains all the variables, buffers and data

structures that can't fit on-chip. It is principally addressed by the 16-bit Data Pointer

(DPTR), although the first two general purpose register (R0, R1) of the currently selected

register bank can access a 256-byte bank of External Data memory. The maximum size

of the External Data Memory space is 64Kbytes. External data memory can only be

accessed using the indirect addressing mode with the DPTR, R0 or R1.

The Internal Data Memory space is functionally the most important data memory

space. It resides up to four banks of general purpose registers, the program stack, 128

bits of the 256-bit memory, and all the variables and data structures that are operated on

directly by the program. The maximum size of the Internal Data Memory space is 256-

bytes. However, different 8051 family members integrate different amounts of this

memory space on chip.

The register implicit, indirect and direct addressing modes can be used in different parts of the Internal Data Memory space.

The Special Function Register space contains all the on-chip peripheral I/O

registers as well as particular registers that need program access. These registers

include the Stack Pointer, the PSW and the Accumulator. The maximum number of

Special Function Registers (SFR’s) is 128, though the actual number on a particular

8051 family member depends on the number and type of peripheral functions integrated on-chip.

The SFRs all have addresses greater than 127 and overlap the address space of the

upper 128 bytes of the Internal Data Memory space. The two memory spaces are

differentiated by addressing mode. The SFRs can only be accessed using the Direct

addressing mode while the upper 128 bytes of the Internal Data Memory (if integrated

on-chip) can only be accessed using the Indirect addressing mode.

(c) Light Emitting Diode (LED):

A light-emitting diode (LED) is a semiconductor light source. The color of the light is determined by the energy gap of the semiconductor.

PRINCIPLE :

When a light-emitting diode is forward biased electrons are able to recombine with

electron holes within the device, releasing energy in the form of photons. This effect is called

electroluminescence. Electroluminescence (EL) is an optical and electrical phenomenon in

which a material emits light in response to the passage of an electric current or to a strong

electric field. The wavelength of the light emitted, and thus its color depends on the band gap

energy of the materials forming the p-n junction. The materials used for the LED have a

direct band gap with energies corresponding to near-infrared, visible or near-ultraviolet light.

CONSTRUCTION :

LEDs are usually built on an n-type substrate, with an electrode attached to the p-type

layer deposited on its surface. P-type substrates, while less common, occur as well. Many

commercial LEDs, especially GaN/InGaN, also use sapphire substrate. Most materials used

for LED production have very high refractive indices. Light extraction in LEDs is an

important aspect of LED production.

(d) DISPLAY:

A seven-segment display, is a electronic display device for displaying decimal

numerals. A seven segment display is composed of seven elements. Individually on or

off, they can be combined to produce simplified representations of the Arabic numerals.

The set values and the selected time intervals are shown on the 7-

segment display. There are two types of displays available. One is common anode type display and the other is common cathode type display.

In common cathode type display all the cathodes of the segments are tied

together and connected to ground. The supply will be given to the required segment

from the decoder or driver.

In common anode type display the anodes of all the segments are tied together

and connected to supply and the required segments will be connected to ground from

the decoder or driver.

In this project common anode type display (H101A) is used. Port 1 is used for the seven segment data.

The seven segments are arranged as a rectangle of two vertical segments on

each side with one horizontal segment on the top, middle, and bottom. Additionally, the

seventh segment bisects the rectangle horizontally.

In a simple LED package, typically all of the cathodes (negative terminals) or all

of the anodes (positive terminals) of the segment LEDs are connected together and

brought out to a common pin; this is referred to as a "common cathode" or "common

anode" device. Hence a 7 segment plus decimal point package will only require nine

pins.

A single byte can encode the full state of a 7-

segment-display. The most popular bit encodings are gfedcba

and abcdefg - both usually assume 0 is off and 1 is on.

This table gives the hexadecimal encodings for

displaying the digits 0 to 9:

Digit

0 0x3F 0x7E on on on on on on off1 0x06 0x30 off on on off off off off2 0x5B 0x6D on on off on on off on3 0x4F 0x79 on on on on off off on4 0x66 0x33 off on on off off on on5 0x6D 0x5B on off on on off on on6 0x7D 0x5F on off on on on on on7 0x07 0x70 on on on off off off off8 0x7F 0x7F on on on on on on on9 0x6F 0x7B on on on on off on on

In this project seven segment display is connected to pins of Port 1. Common Anode

Connection is suitable for this application. The timer of microcontroller is interfaced with seven

segment display to display the delay of light.

The decoder enhances the capability of accommodation for more number of seven segment

displays with the same number of port pins. The current limiting resistor associated with each

segment limits the current at the cost of illumination. The drop across each segment will be 2v

approximately. The maximum current that the segment can handle is 10mA. Care must be taken to

limit the current to less than 10mA by proper selection of resistor.

Current drawn by segment

= (Supply voltage – Drop across segment) / Resistance

= (5v - 2v)/1k = 3mA.

Common cathode 7-segment:

In this design, we are about to use a Common Cathode 7-segment in which the LED’s are

connected in a manner sourcing from the Microcontroller. As you can see in the above pin

configuration there is two common ground pins, we can use any one of it. The 7-segment should be

connected to the port in the following order P2.0 to pin “a” of the 7 segment, P2.1 to b , P2.2 to c and

ends up with P2.7 to h. These are the connection configurations and components we are going to

use in this 4-way Traffic light system using 8051 Microcontroller

DESIGN:

The above diagram illustrates the traffic flow layout of the four way road. And this is just a model of

the four way road ,schemes and layout may subjected to change. I have chose this one for easier

explanation of the traffic flow.

The traffic flow can be classified in to four phases in the above diagram and i have considered the North

as starting point of this traffic flow. And in the above scheme vehicles are allowed to make a free right turn

so we need to consider only two directions straight and left. So the green signal was classified into two

types one for G for permitting vehicle to proceed forward and GL for permitting vehicles to left.

PHASE I-

Initially Vehicle from A needs to travel to F and from E to B roads.

So in the first Phase forward green signal in A and E permits vehicles to pass through while East and west roads are stopped by red signal.

PHASE II-

Phase II permits the vehicle to pass from G to D and from C to H roads.

Traffic flow from rest of the two roads North and south was stopped by means of Red signal.

PHASE III-

Phase three permits traffic flow in the left directions from A to D and from E to H. Traffic flow in East and west are stopped by means of red signal.

PHASE IV-

Phase four permits traffic flow from C to F and from G to B.

Traffic flow in the North and south are stopped by means of red signal.

The cycle repeats again from Phase I to Phase IV and thus the traffic is regulated.

7. SOFTWARE

#include<reg51.h>

void timer()

TF0=0;

TMOD=0X01;

TH0=0X3C;

TL0=0X60;

TR0=1;

while(TF0==0);

TF0=0;

void delay(unsigned int sec)

unsigned int i,j;

for(i=0;i<=sec;i++)

for(j=0;j<=10;j++)

timer();

void disp(unsigned int a)

int j;

unsigned int i[]=0XC0,0XF9,0XA4,0XB0,0X99,0X92,0X82,0XF8,0X80,0X98;

for(j=a;j>=0;j--)

P1=i[j];

delay(1);

void main()

while(1)

P2=0x87;

P3=0xFF;

disp(9);

P3=0x30;

disp(2);

P2=0x4b;

P3=0xFF;

disp(9);

P3=0x90;

disp(2);

P2=0x2D;

P3=0xFF;

disp(9);

P3=0xC0;

disp(2);

P2=0x1E;

P3=0xFF;

disp(9);

P3=0x60;

disp(2);

8. COMPONENTS REQUIRED

1. Micro Controller 89c51 1 No

2. Crystal Oscillator 12 MHz 1 No

3. Light Emitting Diodes Red 4 Nos

Orange 4 Nos

Green 4 Nos

4. Resistors 1 kΩ 4 Nos

460 Ω 4 Nos

100 Ω 4 Nos

120 Ω 10 Nos

5. Capacitors 33pF 2 Nos

6. Miscellaneous Components:

ƒ Regulated Power Supply of 5V

ƒ Circuit Connecting Board

ƒ Connecting Wires

9. FUTURE SCOPE

This project can be enhanced in such away as to control automatically the

signals depending on the traffic density on the roads using sensors like IR

detector/receiver module extended with automatic turn off when no vehicles are

running on any side of the road which helps in power consumption saving.

This proximity detector using an infrared detector shown in fig.1 can be

used in various equipment like automatic door openers and burglar alarms. The

circuit primarily consists of an infrared transmitter and an infrared receiver. The

transmitter section consists of a 555 timer IC functioning in a stable mode. It is

wired as shown in the fig. 2. The output from a stable is fed to an infrared LED via

resistor R4, which limits its operating current. This circuit provides a frequency

output of 38 kHz at 50 per cent duty cycle, which is required for the infrared

detector/receiver module.

The receiver section comprises an infrared receiver module, a 555 mono

stable multi vibrator, and an LED indicator. Upon reception of infrared signals,

555 timer (mono) turns on and remains on as long as infrared signals are

received. When the signals are interrupted, the mono goes off after a few

seconds (period=1.1 R7xC6) depending upon the value of R7-C6 combination. Thus if R7=470 kilo-ohms and

C6=4.7μF, the mono period will be around 2.5 seconds.

Both the transmitter and the receiver parts can be mounted on a single

breadboard or PCB. The infrared receiver must be placed behind the infrared

LED to avoid false indication due to infrared leakage. An object moving nearby

actually reflects the infrared rays emitted by the infrared LED. The infrared

receiver has sensitivity angle (lobe) of 0-60 degrees, hence when the reflected IR

ray is sensed, the mono in the receiver part is triggered. The output from the

mono may be used in any desired fashion. For example, it can be used to turn on

a light when a person comes nearby by energizing a relay. The light would

automatically turn off after some time as the person moves away and the mono

pulse period is over. The sensitivity of the detector depends on current-limiting

resistor R4 in series with the infrared LED. Range is approximately 40 cm. For

20-ohm value of R4 the object at 25 cm can be sensed, while for 30-ohm value of R4 the sensing range reduces by 22.5 cm.

IR RECEIVER CIRCUIT

TRAFFIC LIGHT CONTROL MODULE USING SENSORS

10. BIBLIOGRAPHY

1. The 8051 Micro controller and Embedded Systems

- Muhammad Ali Mazidi & Janice Gillispie Mazidi

2. Micro controllers Theory and Applications

- Ajay V. Deshmukh

3. www.wikipedia.org

4. www.8051.com

5. www.8052.com

6. www.microcontroller.c